46 



GEOLOGY OF THE THIRD DISTRICT. 



change in the mineral character, but they are accompanied by other fossils which had no 

 existence in the Trenton rock. Fossil-like minerals have also a two-fold character ; one 

 which depends upon themselves as individuals, the other from association. 



As a point or term of comparison for distant localities, the Trenton limestone, from the 

 number of its fossils, as to class, genera, species and individuals, is one of the most important 

 rocks of the lower part of the New- York system. In parts, it is loaded with the remains of 

 animal Ufe. In the preceding rocks there was but the dawn ; in this, a full existence as to 

 different kinds, and numbers especially of different kinds. 



-^ ' •» i 



The fossil No. 2 of the wood-cut, Strophomena deltoidea, and of the Reports, is an exceed- 

 ingly abundant fossil in this rock ; and as far as a knowledge of its range has been acquired 

 cither in this State or elsewhere, it is restricted to it, and is therefore a characteristic fossil. 

 It is in greatest number at Trenton falls, and the range generally of this limestone in Oneida 

 county. 



In a work like that of the survey of a State, where the object is to diffuse knowledge 

 amongst the many, and not to the few only, a departure from common usage, where the 

 obvious tendency was exclusive, should be made, be it ever so venerable from age, provided 

 that the subject thereby is rendered "simple and easy to be acquired. To attain this object, 

 the specific name of the fossils will precede the generic ones as in our common language, 

 and for the reason that the name of the species is more frequently used than that of the genus. 

 The name, in all cases where new or doubtful, will be taken from the rock or group where it 

 exists, or a locality equally characteristic. All received specific names vrill be rendered in 

 the common language, as Deltoid strophomena for No. 2 of the wood-cut, no change what- 

 ever being made in those of the genera. 



No. 3. The Puffball favosite (Favosites lycopodites), from its resemblance to that common 

 fungus, is also highly characteristic, and is in great numbers ; but it is found also in the lower 

 part of the Utica slate, where it ends. It is one mass of small angular cells, arranged side 



